Disk arrays are also referred to as RAIDs (Redundancy Arrays of Independent (Inexpensive) Disks) and have a configuration in which a plurality of disks are arranged in an array form. By appending redundancy data to data, reliability of the disk array is improved. The RAID includes a RAID0 in which by striping, for example, a plurality of disks are used as if it were one disk, a RAID1 in which using mirroring, the same data is written to a plurality of disks, a RAID5 in which by recording data and parities on a plurality of disks, fault tolerance is improved, and the like. Among these disks, in the RAID5, parity information for error correction is generated when the data is written to the disks. This parity information is distributed across and written to the disks with the remaining data by the striping. The number of the disks required for the parities is set to one. With this arrangement, even if one disk has failed, the data can be restored using the data and the parities in the remainder of the disks.
When a RAID controller detects a failure of a disk in conventional disk arrays, the conventional disk arrays have a function of performing replacement to a spare disk and rebuilding (rebuilding) data on the failed disk onto the replacement disk. On that occasion, using disks other than the replaced disk among plural disks constituting the disk array, data on the replacement disk is prepared.
In a disk array system for which high availability is required, it is necessary to rebuild data onto a replacement disk after replacement of a failed disk, in parallel with a normal operation (unless the normal operation is performed at the time of rebuilding, business is disturbed). At the time of parity rebuilding after the replacement of the disk, it is necessary to read data from all of disks that belongs to a parity group, other than the replaced disk. Thus, access performance is normally degraded. When the number of data drives is increased in a configuration such as the RAIDs constituting the parity group, the performance will be further degraded.
FIG. 10 is a schematic diagram showing a typical configuration example of a conventional disk array system. Referring to FIG. 10, an access module 14 serves as an interface for transmitting and receiving a command, data, and a control signal between a host 20 and a disk array. A RAID module 13 is constituted from the RAID controller and management software, and performs a read/write, fault detection, processing for disk rebuilding, and the like on data on a plurality of disks 111 to 11n of a redundant configuration. A disk access bus 12 provides connecting paths between a plurality of disk drives 111 to 11n and the RAID controller 13. Incidentally, rebuilding of a disk drive is performed on the array of the redundant configuration such as the RAID 1, 5, or 10. Each of the disk drives 111 to 11n is constituted from the disk drive such as an HDD (Hard Disk Drive), and is abbreviated as a “disk”.
Patent Document 1 discloses a configuration in which in order to suppress further degradation of the performance when a number of data drives n is increased in an nD+1P representing a disk configuration such as the RAID constituting the parity group, copying is performed from one disk regardless of the number n. Patent Document 2 describes rebuilding (rebuilding) onto a disk by the RAID controller. A rebuild rate (Rebuild Rate) of a failed disk of 100% means that the system is all applied to the rebuilding of the failed disk. The rebuild rate of 0% means that the system performs rebuilding of the failed disk during an idle time when the system performs no other operation. A default rebuild rate is set to approximately 30% or the like, for example.
[Patent Document 1]
JP Patent Kokai Publication No. JP-P2002-108571A
[Patent Document 2]
JP Patent Kokai Publication No. JP-P2004-38290A